Growing Comfrey

Latest Update 23rd July 2016.

Comfrey
  • Comfrey is lush and fast-growing and the whole plant is an excellent soil conditioner.  
  • The roots reach deep into the subsoil accessing minerals out of reach of most other plants in the garden.  These minerals, which have been leached out of the topsoil by rain, can be recycled.
  • If kept well fed and watered Comfrey will provide an excellent supply of leaves for the compost, as a mulch or made into a rich liquid fertiliser.  The leaves have a highly beneficial concentration of potassium, nitrogen, iron, magnesium, calcium, silica, and are very high in protein.
  • The flowers are an excellent bee attractant. 
Details.
  • Variety:                                                  Symphytum x Uplandicum.
  • Family group:                                         Boraginaceae.
  • Garden bed type:                                     Drip line irrigation.
  • Recommended soil pH.                           6.0 - 7.0.
  • Minimum sun per day:                            3 hours.
  • Plant spacings (centres):                        500mm.
  • Climate:                                                  Warm temperate.
  • Geography:                                             Southern hemisphere.
Growing Conditions.
  • Comfrey needs full sun.
  • Its dormant in winter and needs winter chill to set flowers later in the season.
  • It grows well in moist fertile soil, but can stand hot weather because of its roots, which access water deep in the soil.
Soil Preparation.
  • Clear a space in spring by removing old mulch, dead leaves and unwanted organic material.  Choose a place where it has not been grown for several years. 
  • Apply a 60mm top dressing of homemade compost. and cover with about 50mm of straw mulch.
Growing Instructions.
  • I have always propagated comfrey from seeds sown in mini pots in the propagator, and transplanted them as seedlings in a prepared bed.
  • Alternatively, comfrey can be propagated from root cuttings or by crown division. Root cuttings are made by cutting pieces of root about 250mm long in Autumn and bury them on their side 25mm deep in a compost propagator.
  • When they shoot in spring, transplant them into the prepared bed.
  • Comfrey should not be moved once established, as any pieces of root left behind will produce new plants.
  • To remove a comfrey plant, bury the whole plant under a layer of wet newspapers and a thick layer of mulch.  This rots the comfrey plant leaving very rich soil in its place.
  • Care must be taken not to allow the comfrey plants to become hard to control weeds.
  • To maintain fast lush growth, make sure you keep the soil surrounding your comfrey plants moist, especially in hot dry weather.  
  • Once the plant starts to grow vigorously apply a foliar spray of aerated compost tea every 4 weeks.
Harvesting and Storage
  • I harvest comfrey for use in the worm farms in my Ecobeds and as a stimulant in my compost heap.
  • Comfrey has medicinal properties, and was used traditionally for both internal and external use.  Unfortunately it has been found to cause liver toxicity and is now regarded as a poison if ingested.
  • For this reason, I don't use comfrey in the kitchen or in the medical cabinet, but it is still a nutritional powerhouse when incorporated into soil.
Organic Pest Control.
  • Greenhouse whitefly.  
    • Aerated compost tea improves this plant's resistance to whitefly damage.
    • Exclusion netting is very effective against whitefly, but they are small and will occasionally breach your defences, so you need to check your crop regularly.  
    • Control any infestations by spray your crop thoroughly with organic horticultural oil (Eco-oil in Australia).
    • Spray again in a few days to ensure second generation whitefly do not survive.
  • Aphids (greenfly). 
    • Use the same method described above for whitefly.
  • General.
    • Repeated foliar sprays of aerated compost tea should deter most airborne pests and diseases.
    • Proper soil preparation and regular applications of home made compost should control soil borne pests.